Amine addition salts of nitro-carboxyalkali metal phenolates



United States Patent 3,420,874 AMINE ADDITION SALTS 0F NITRO-CARBOXY-ALKALI METAL PHENOLATES Lionel A. Henderson, Columbus, Ind., assignor toStandard Oil Company, Chicago, 111., a corporation of Indiana NoDrawing. Filed Sept. 28, 1962, Ser. No. 227,048 US. Cl. 260501.14 3Claims Int. Cl. C07c 101/44; C06 9/02 This invention relates to thenovel compounds nitroaminocarboxy-alkali metal phenolates and toammonium nitrate propellant compositions utilizing these compounds as acombustion catalyst.

In ammonium nitrate compositions formed from an oxidizable organicbinder material which functions as a matrix for ammonium nitrateparticles, it is necessary to promote the combustion of the mixture bymeans of a catalyst. Many catalysts are known for this purpose rangingfrom the very old inorganic chromium compounds such as ammoniumdichromate to recently discovered alkali metal salts of certain organicacids and even completely organic compounds. The Prussian blues are ofinterest in high burning rate propellants, but these like the chromiumcompounds, produce reaction products which are solid materials whichcause severe nozzle erosion. The alkali metal catalysts react to formalkali metal carbonates which, while not particularly erosive, do resultin an objectionable accumulation of ash in certain uses such as in gasgenerator use in connection with auxiliary power systems.

For propellant purposes, it is very desirable that the burning rate ofthe propellant show a minimum effect with variation in combustionchamber pressure. This effect of pressure on burning rate is commonlyspoken of as the pressure exponent having the symbol n. The smaller thesize of n, the less effect of pressure on the burning rate. The burningrate is aifected by the temperature of the propellant mass. In general,the lower the temperature of the mass, the lower the burning rate. It isdesirable that this temperature coefficient, like the pressure exponent,be low. The ultimate would be a situation in which the burning ratewould be independent of pressure and temperature.

In general, the better known combustion catalysts have no influence onthe characteristics of the propellant and function solely with respectto the rate of burning. Dependent upon the oxidizable organic bindermaterial present, there commonly exists a problem with respect toignition of the propellant at lower atmospheric temperatures.Frequently, it is necessary to introduce additives into the propellantcomposition to improve ignitabilit at these lower atmospherictemperatures which may be 20 to -75 F. For some installations, it isnecessary that the propellant deliver gas smoothly and uniformly for along period of time. It is common to use low burning rate propellants inthese situations. Unfortunately, -with the prior art catalysts at lowburning rates, it is difficult to maintain smooth, uniform burning.Still more unfortunately, it is very difiicult to overcome this problemby the addition of other compounds which improve burning smoothnesswithout simultaneously harming the other characteristics of thepropellant composition.

A novel class of compounds has been discovered. These compounds act ascombustion catalysts for ammonium nitrate propellant compositions.Compositions containing these compounds have superior ignitabilitycharacteristics at even the lowest of atmospheric temperatures.Propellant compositions containing these compounds have superior,smooth, uniform burning characteristics at low burning rates. Propellantcompositions containing these Patented Jan. 7, 1969 compounds give muchless ash formation at a given burning rate than do the best previouslyknown alkali metal containing organic compounds which function ascombustion catalysts.

The novel class of chemical compounds of the invention may be broadlydescribed as mixed salts of nitrocarboxyhydroxybenzene(nitromonocarboxylphenol or nitromonohydroxylbenzoic acid). In thecompounds of the invention, the carboxyl group is reacted with anorganic compound containing an amino group; the hydroxyl group isreacted with an alkali metal. The nitrosalicylic acids are especiallysuitable for the preparation of ammonium nitrate combustion catalysts.In addition to one or more nitro groups, the benzene nucleus may includealkyl substituents. It is to be understood that the novel class ofcompounds of the invention includes not only the compounds containing asingle substituted benzene nucleus, but also two such nuclei which arejoined by an alkylene bridge. Illustrative of such a compound which canbe used to produce an exceptional ammonium nitrate combustion catalystis dinitromethylene disalicylic acid.

Broadly, the compounds of the invention fall into two subclasses:nitro-aminocarboxy-alkali metal phenolate or alkylenedi(nitro-aminocarboxy-alkali metal phenolate) where the alkylene grouphas 1-3 carbon atoms, i.e., methylene, ethylene or propylene. Any of thealkali metals may be used in forming the compounds of the invention. Foruse as a combustion catalyst, a sodium salt is especially suitable. Anyorganic compound containing an.

amino group may be used in forming the compound of the invention. Theamines which contain carbon, hydrogen and nitrogen atoms and the aminescontaining carbon, hydrogen, oxygen and nitrogen atoms are especiallysuitable. The amines which are strongly basic are preferred when thecomposition needs exceptionable storage sta bility. Illustrative ofespecially suitable amines for the preparation of the catalyst used inthe composition of the invention are ethylene diamine, monoethanolamine,diethylene diamine (piperazine) and guanidine.

Illustrative compounds of the invention based upon the reaction productsof 3,5-dinitrosalicylic acid where the carboxyl group is in the 1position are: the reaction product with guanidine and sodium methoxideis 3,5-dinitro-1- guanidiniumcarboxy-2-sodium phenolate. The reactionproduct with 1 mole of ethylene diamine, 2 moles of sodium methoxide and2 moles of acid is diethylene diamino bis(carboxy-3,5-dinitro-2-sodiumphenolate). The reaction product with 1 mole of ethylene diamine, 2moles of sodium methoxide and 2 moles of acid is ethylene diaminobis(carboxy-3,5-dinitro-2-sodium phenolate). The reaction product of5,5-methylene-di(3,5-dinitrosalicylic acid) with guanidine and sodiummethoxide is 5,5- methylene di(3,3' nitro 1,1guanidiniumcarboxy-2,2-sodium phenolate). It is to be understood that the scope of thecompounds of the invention are not limited to the illustrative compoundsset forth above, but include the class as broadly defined above.

When a compound of the invention is utilized as a catalyst for promotingthe burning rate of ammonium nitrate propellant compositions, enoughmust be introduced into the composition to obtain a burning ratepromotion. The amount of catalyst used is also influenced by the rate ofburning desired. The more catalyst present, to a degree, the faster therate of combustion of the composition. (It is to be understood that theburning rate is also affected by the particular oxidizable organicbinder material present.) In general, the composition will containbetween about 0.1 and 15 Weight percent of the catalyst. (Hereinafterall percentages are to be understood as weight percent.) With thethermoplastic matrix formers or binders obtained from cellulose estersand plasticizers therefor, between about 1 and 7% of catalyst producessatisfactory burning rates for typical military gas generation androcketry usages.

The ammonium nitrate propellant composition utilizes as a catalystbroadly about 0.ll weight percent of the above defined mixed salt; about1()4O weight percent of oxidizable organic binder material; and ammoniumnitrate as the major component. Other catalysts and additives may alsobe present.

The ammonium nitrate may be the high purity material commonly producedby synthetic plants today, or it may be technical grade containing smallamounts of inorganic impurities. In addition to the ammonium nitrate,for special purposes, sodium nitrate or potassium nitrate maybe presentin an appreciable amount. The decomposition rate of the ammonium nitrateis influenced by the particle size. For gas generation purposes, theammonium nitrate is finely divided. Particularly suitable ammoniumnitrate will contain about 80 weight percent of material having a screensize greater than 80 mesh and smaller than 30 mesh. The more finelypowdered ammonium nitrate is used where higher burning rates aredesired. Usually the propellant composition will contain between about60 and about 80% of ammonium nitrate. In all cases, the major componentpresent in the composition is ammonium nitrate.

In order to permit the shaping of the ammonium nitrate composition intodefinite configurations, a matrix former or binder material is present.When ammonium nitrate decomposes, free-oxygen is released. The existenceof this free-oxygen permits oxidizable organic materials to be used asthe binders and thereby obtain additional gas production. Theseoxidizable organic materials may contain only carbon and hydrogen, forexample, high molecular weight hydrocarbons such as asphalts orresiduums, and rubbers, either natural or synthetic. Or, it may containother elements in addition to carbon and hydrogen, for example, as inThiokol rubber and neoprene. The stoichiometry of the composition isimproved, with respect to smoke production, by the use of organicmaterials containing combined oxygen as the binders. The binder ormatrix former may be a single compound such as a rubber or asphalt or itmay be a mixture of compounds. The mixtures are particularly suitablewhen special characteristics are to be imparted to the propellant whichcannot be obtained by the use of a single compound.

Multi-component binder, or matrix former, consists of a polymeric basematerial and a plasticizer therefor. Particularly suitable polymericbase materials are cellulose esters of alkanoic acids containing from 2to 4 carbon atoms such as cellulose acetate, cellulose acetate butynateand cellulose propionate. The polyvinyl resins such as polyvinylchlorideand polyvinyl acetate are good bases. Styreneacrylonitrile is an exampleof a copolymer which forms a good base material. Polyacrylonitrile isanother suitable base material.

The plasticizer component of the binder also, preferably, containscombined oxygen. The oxygen may be present in the plasticizer as anether linkage and/or hydroxyl and/or carboxyl; also the oxygen may bepresent as a part of an inorganic suhstituent, particularly, a nitrogroup. In general, any plasticizer which is adapted to plasticize theparticular polymer may be used in the invention. A single plasticizingcompound may be used; more usually two or more compounds are used inconjunction. Exemplary classes of plasticizers which are suitable areset out below. (It is to be understood that these classes areillustrative only and do not limit the types of organic compounds whichmay be used to plasticize the polymer.)

Di-lower alkyl-phthalates, e.g., dimethyl phthalate, dibutyl phthalatedioctyl phthalate and dimethyl nitrophthalate.

Nitrobenzenes, e.g., nitrobenzene, dinitrobenzene, nitrotoluene,dinitrotoluene, nitroxylene, and nitrodiphenyl.

Nitrodiphenyl ethers( e.g., nitrodiphenyl ether and 2,4-

dinitrodiphenyl ether.

Tri-lower alkyl-citrates, e.g., triethyl citrate, tributyl citrate andtriamyl citrate.

Acyl tri-lower alkyl-citrates where the acyl group contains 24 carbonatoms, e.g., acetyl triethyl citrate and acetyl tributyl citrate.

Glycerol-lower alkanoates, e.g., monoacetin, triacetin,

glycerol tripropionate and glycerol tributyrate.

Lower alkylene-glycol-lower alkanoates wherein the glycol portion has amolecular weight below about 200, e.g., ethylene glycol diacetate,triethylene glycol dihexoate, triethylene glycol. dioctoate,polyethylene glycol dioctoate, dipropylene glycol diacetate, nitromethylpropanediol diacetate, hydroxyethyl acetate and hydroxy propyl acetate(propylene glycol monoacetate).

Dinitrophenyl-lower alkyl-lower alkanoates, e.g., dinitrophenylethylacetate, and dinitrophenyl amyloctoate.

Lower alkylene-glycols wherein the molecular weight is below about 2.00,e.g., diethylene glycol, polyethylene glycol (200), and tetrapropyleneglycol.

Lower alkylene-glycol oxalates, e.g., diethylene glycol oxalate andpolyethylene glycol (200) oxalate.

Lower alkylene-glycol maleates, e.g., ethylene glycol m aleate andBis-(diethylene glycol monoethyl ether) maleate.

Lower alkylene-glycol diglycolates, e.g., ethylene glycol diglycolateand diethylene glycol diglycolate.

Miscellaneous diglycollates, e.g., dibutyl diglycollate, dimethylalkyldiglycollate and methylcarbitol diglycollate.

Lower alkyl-phth-alyl-lower alkyl-glycollate, e.g., methyl phthalylethyl glycollate, ethyl phthalyl ethyl glycollate and butyl phthalylbutyl glycollate.

Di-lower alkyloxy-tetraglycol, e.g., dimethoxy tetra glycol and dibutoxytetra glycol.

Nitrophenylether of lower alkylene glycols, e.g., dinitrophenyl ether oftriethylene glycol and nitrophenyl ether of polypropylene glycol.

Nitrophenoxy alkanols wherein the alkanol portion is derived from aglycol having a molecular weight of not more than about 200. These maybe pure compounds or admixed with major componentbis(nitrophenoxy)alkane.

In addition to the main components, i.e., ammonium nitrate binder andcatalyst, the propellant composition may contain other components. Forexample, materials may be present to improve low temperatureignitability, for instance, oximes or asphalt; surfactants may bepresent in order to improve the adhesion of the nitrate and thebinderalso to improve the shape retention characteristics of thecomposition; burning rate promoters which are not considered to be truecatalysts such as finely divided carbon may be present. Aromatichydrocarbon amines such as toluene diamine, diphenyl amine, naphthalenediamine, and toluene triamine may be present. In order to improvestorage stability, particularly at higher atmospheric temperatures,between about 0.1% and 1% of N-phenylmorpholine will be present.

A particularly good composition consists of cellulose acetate, about6-12%; acetyltriethylcitrate, about 6-12%; dinitrophenoxyeth'anol, about612; carbon, about 26%; toluene diamine, about 0.00.5%;N-phenylmorpholine, about 0.5%; catalyst, about 17% and the remainderammonium nitrate.

It has been observed that propellant compositions containing one of thedefined compounds of the invention and also an alkali metal barbituratehave exceptionally low pressure exponents and simultaneously very goodtemperature coefficients. In general, these results are obtained usingabout equal weight amounts of the mixed salt of this invention andalkali metal barbiturate with the total amount of the two compoundsbeing between about 2 and 7 weight percent. An especially suitablecombination is formed by monosodium barbiturate and the guanidinesodiummixed salt of 3,5-dinitrosalicy1ic acid.

Although the burning rate at equal weight content is somewhat lower thanwith the mononuclear compounds, the alkylene bridge dinuclear compoundsgive exceptionally low pressure exponents and very satisfactorily lowtemperature coeflicients. For these reasons, compositions containingsuch mixed salts are suitable for military use where the compositionwill be fired over a wide range of atmospheric temperatures.

Illustrations The mixed salts of the invention are easily prepared byreaction in a common solvent for the particular acid, the particularamine and the alkali metal affording reactant. Methanol is aparticularly good solvent reaction medium and a methoxide as the alkalimetal afiording reagent. A reaction medium can be readily selectedwherein the product precipitates out in crystalline form. Purity of theproduct can be determined easily by measuring the melting point of thecrystals. It has been found by means of infrared inspection, regardlessof which agent-amine or alkali metalis used first in the reaction, thefinal product has the amino group attached to the carboxy group' and thealkali metal attached to the hydroxy group. Compounds were prepared byreacting equal moles of guanidine and sodium methoxide with3,5-dinitrosalicylic acid; reacting 2 mols of the 3,5-dinitrosalicylicacid with 1 mol of diethylene diamine (piperazine); 2 mols of the 3,5-dinitrosalicylic acid with ethylene diamine; 2 mols of guanidine with 1mol of 3,3'-dinitro-5,5'-methylene disalicylic acidin each instance thetheoretical amount of sodium methoxide was added. In all cases,essentially the theoretical yield of mixed product was obtained in theform of crystalline solids. The position of the sodium and amino groupwas determined by infrared spectrographic analysis of the crystallinesolid.

The compounds were found to be effective burning rate catalysts forammonium nitrate propellant compositions. Comparative compositions wereprepared in a one quart laboratory mixer; each composition was mixedtogether for one hour at a temperature of about 212 F. Celluloseacetate, analyzing about 55% of acetic acid equivalent, was used inconjunction with essentially pure dinitrophenoxyethanol land acetyltriethyl citrate plasticizers.

After the completion of the mixing, the pasty mass was compressionmolded into a slab /2" in thickness. The slab was permitted to cool toroom temperature and sawed into strips for use in the Crawford Bom'bburning rate tests. Tests were carried out at diiferent pressures inorder to determine the pressure exponent n for each composition.

Tests were run to determine the temperature coefiicient r of eachcomposition. Temperature coefiicients were obtained at both constantpressure and constant nozzle size. In these tests, a propellant strandwas brought to the desired test temperature by storage at thattemperature until the entire mass of propellant was certain to be at thedesired temperature. The ease of ignition and the smoothness and theuniformity of burning of the propellants was also observed.

In this series of tests, the component analysis of compositions testedwas:

Mark 6205 contained the sodium guanidine mixed salt of3,5-dinitrosalicylic acid. Mark 6206 contained the sodium-piperaz-inemixed salt of 3,5-dinitrosalicylic acid. Mark 6207 contained thesodium-ethylene diamine mixed Mark Burning rate n 0' 1r 1:

The above data establish that the mixed salt compounds of the inventioncontaining less thanone-hal-f the sodium metal content of sodiumbarbiturate have as good or better burning rates. These compositionsalso have better pressure exponents and as good or better temperature00- eflicients. The three compositions of the invention ignited easilyat the lowest temperatures and burned smoothly.

A propellant composition, designated as Mark 6217, was prepared using asthe catalyst the reaction product of guanidine, sodium methoxide and3,3-dinitro-5,5 methylene disalicylic acid in a mole ratio of 212:1.This composition was prepared as described above using a 1 quart mixerwith a 40 minute agitation time. The component composition ofcomposition Mark 6217 was:

second with a pressure exponent of 0.487. The temperature coefiiclent, uwas 0.075 and the temperature coeflic ent, 'n' was 0.148. By comparisonwith the characterist1cs shown in an earlier composition, Mark 6217 hasa desirably low pressure exponent and desirably low tem peraturecoeflicient, 1r

Composition Mark 6214 included, as the catalyst, the mixed salt sodiumguanidine dinitrosalicylate made as described previously and alsomonosodium barbiturate. The component formulation of Mark 6214 was:

A Percent mmomum n1trate 61.00 Cellulose acetate 9 79 Acetyl triethylcitrate 11:25 Dinltrophenoxyethanol (28% diether) 990 Carbon 3 00 Sodiumguanidine dinitro-salicylate 2 06 Monosodium barbiturate 2 00N-phenylmorpholine u 0 50 Toluene diamine u 0 50 Composition Mark 6214gave a burning rate of 0.070 with a pressure exponent of 0.466. Thetemperature coeflic1ent,a was 0.100 and the temperature coefficient, 1rwas 0.19. The pressure exponent was unusually low considering the amountof monosodium barbiturate catalyst present; indeed this pressureexponent is markedly lower than that given by the catalysts set forthearlier. It 1s also evident that this particular composition has adesirably lower temperature coefiicient, 1r than does the compositioncontaining only monosodium barbiturate as a catalyst-Mark 6209.

Thus having described the invention, what is claimed is: 1 1.3,5-dinitro-1-guanidiniumcarboxy-2-sodium phenoate.

2. Ethylene diamino bis(carboxy-3,S-dinitro-Z-sodium phenolate) 3.5,5'-methylene-di(3,3'-nitro 1,1 guanidiniumcarboxy-2,2-sodiumphenolate) References Cited UNITED STATES PATENTS Erickson 260268 Westonet a1. 260268 Gagliardi 260501 Goldberg 260501 Larrabee 260501 La Fontet a1 260501 Mackay 260564 Hageman 260564 Gallaghan 2605 64 8 3,056,70210/1962 Linsk 149-19 3,056,703 10/ 1962 Korpics 149--19 FOREIGN PATENTS591,808 4/1931 Germany.

OTHER REFERENCES Graig et 211., Progress in Drug Research, vol. 3, pp.116-150, p. 116 relied on (1961).

LEON ZITVER, Primary Examiner.

M. W. GLYNN, Assistant Examiner.

U.S. c1. X.R.

zen-501.17, 501.2, 268; 149 19, 55

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,420,874 January 7, 1969 Lionel A. Henderson It is certified that errorappears in the above identified patent and that said Letters Patent arehereby corrected as shown below:

Column 2, line 45, "ethylene diamine" should read piperazine Column 4,line 61, "6-12;" should read 6-l2%; Column 6, lines 24 and 25,"3,3dinitro-S,5 methylene" should read 3,3-dinitro5,5-methylene Signedand sealed this 17th day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR.

1. 3,5-DINITRO-1-GUANIDINIUMCARBOXY-2-SODIUM PHENOLATE.